# 15 Hongzhen: Nitrogen use efficiencies of biobased fertilisers

Can nitrogen mineral fertilisers be replaced by processed and manure-derived biobased fertilisers?

Hongzhen Luo (罗红祯) is a PhD fellow at Ghent University (UGent). She conducts research on biobased fertilisers derived from animal manure and on their ability to replace mineral fertilisers. With her research she aims to contribute to closing nutrient loops in agriculture.

Department & Group: Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent university.

Supervisors: Prof. Erik Meers and prof. Stefaan De Neve (Ghent University)

Dissertation title:

Interrelations between the nitrogen availability of biobased fertilizers and the dynamics of the plant-soil system

Topic – in brief

  • Laboratory and field experiments on biobased fertilisers derived from animal manure to study their interactions with soil microbes and crops
  • Can biobased fertilisers replace mineral fertilisers?
  • How would legislation have to facilitate such replacement?

Nitrogen in manure is a valuable nutrient source for crops but when applied in abundance, it can cause environmental problems.

Through processing, the nutrients in manure can be brought into forms that are easier to manage.

Such processing can be: anaerobic digestion, solid-liquid separation, stripping and scrubbing, and membrane filtration – or their combination.

Hongzhen conducts experiment using the recovered fertilisers:

  1. Pot experiment without crops and in the lab. Here the question is: ‘How do microbes interact with the nitrogen in the fertilisers and how do they affect the nitrogen efficiency of the biobased fertilisers?’
  2. Pot experiment with crops and in lab. Here the question is: ‘How is the efficiency of crop-N in-taking of biobased fertilisers as compared to soil microbes?’
  3. Field experiments with crops outside the lab. Here the question is: ‘How do crops develop, when fertilised with biobased fertilisers compared to being fertilised with mineral fertilisers?’


  • Stripping and scrubbing: By increasing the temperature or/and the pH of the manure, liquid ammonium (NH4) changes into gaseous ammonia (NH3). The gas is captured by an acid solution and precipitates into a mineral product.
  • Membrane filtration: is categorised by pore size and is commonly driven by a difference in pressure.
  • PCR (Polymerase chain reaction) test: a test to detect DNA, in her case of microbes. The test provides answers regarding the abundance and occurrence of microbes. What microbes are present in soil, how many and how does their population change over time?


The crops fertilised with biobased fertiliser developed similar to those fertilised with mineral fertiliser.

The competition between crops and microbes is great and microbes seemed to be faster in taking up the nitrogen than the crops – at least shortly after fertilisation and under lab conditions.

Hongzhen’s vision for the future 🙂

To understand microbes and their interaction with fertilisers and plants better to foster food security and maintain the sustainability of agriculture.

Hongzhen’s joys & struggles

Joys: gaining new knowledge, seeing the plants in her experiments grow, doing sports with her colleagues

Struggles: defining her research niche, seeing experiments fail


Benefits of biobased fertilizers as substitutes for synthetic nitrogen fertilizers: Field assessment combining minirhizotron and UAV-based spectrum sensing technologies

Assessing Nitrogen Availability in Biobased Fertilizers: Effect of Vegetation on Mineralization Patterns

If you would like to get in touch with Hongzhen, check out LinkedIn, Research gate or Google Scholar.

Hongzhen’s funding: My PhD research was funded by the EU Horizon 2020 project Nutri2Cycle project (grant number: 773682). Currently, she is working in the projects NutriBudget (https://www.nutribudget.eu/) and NutriKnow (https://www.nutri-know.eu/) projects.

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